Zbikowski was 4-0 in the ring this spring, but he said his desire to play football was greater than his pugilistic ambitions.
"It was time to start the transition back to football," Zbikowski told the Times through text messages. "My teammates are starting to organize some workouts, so it's just time to head back (to Baltimore). Wish I had more time to do both."
Zbikowski, 26, tested positive for THC, the active ingredient in marijuana, after scoring a first-round knockout of Blake Warner on April 23 in Thackerville, Okla. He was suspended by the Chickasaw Nation Boxing Commission, but he later passed a second drug test, and the suspension was lifted.
Bob Arum, Zbikowski's promoter, said the drug test had nothing to do with Zbikowski's decision to return to football training.
"It was a very tough decision for me," Zbikowski said. "It was a tremendous experience fighting for Arum again. (But) as tough as it is to turn yourself into a fighter, it's equally as tough to transition into an NFL player."